There is disclosed in the prior art (U.S. Pat. No. 3,013,917) a method for producing dry transfer of lettering, symbols, indicia, emblems and the like from a substrate sheet to a receptor sheet, by contacting the substrate sheet containing various print, rear side down, with the receptor sheet, and rubbing the substrate sheet, thereby releasing the lettering etc., and transferring the same to the receptor sheet. The substrate sheet may comprise translucent paper, onion skin, films, paper, cellulose acetate and the like. The characters or designs are printed on the rear surface of the sheet, in reverse position as viewed from the rear of the sheet. The rear surface is treated with a release coating to facilitate transfer of the lettering upon application of pressure to the front surface. The patent limits the method by which the ink is applied to the release coated rear surface of the substrate sheet (dry transfer sheet) to: (1) printing in a flat or rotary press; (2) application with a printing brush; or (3) printing with the aid of a silk screen stencil.
The above process has proved to be inadequate in several respects. The process requires huge inventories of typeface because of the many different typefaces which may be required. There are approximately 22,000 different type fonts, not taking into consideration the eight to ten sizes available in each type font, resulting in enormous dealer inventories. The majority of dry transfer sheets are now manufactured by the silk-screen method of reproduction which directly encompasses the above problem of large inventories to the dealers. In addition, it has been found that the quality of print which becomes ultimately adhered to the receptor sheet, has been inadequate. In addition, the time required to produce the transfer sheets has proven to be rather extended.
The high cost associated with the above process has led to a need for a dry transfer technique of lower cost and greater overall quality and efficiency, allowing the consumer the flexibility of making his own transfer as needed.
In accordance with the present invention, there is provided a method, product, and apparatus for forming an electrophotographic image on a carrier sheet, said carrier sheet possessing front and rear surfaces, said image being deposited on the rear surface of said carrier sheet. The carrier sheet composition provides a novel part of this invention. Said image preferably possesses a discernible thickness and, accordingly, upper and lower surfaces, and is further characterized by having pressure-sensitive qualities at least on the upper surface, so that when the rear side of the sheet is brought into contact with a desired surface and pressure is applied to the front side of the carrier sheet, such as by rubbing, a substantially complete transfer of said image from the carrier sheet to the desired surface results. The image, when viewed from the rear of the sheet, is in reverse position and, as viewed from the front of the sheet, is in normal reading position. The present invention overcomes the disdvantages associated with dry transfer systems taught in the prior art and provides an efficient and relatively low-cost method and apparatus for accomplishing the transfer of the heretofore mentioned images from one surface to another without the necessity for maintaining extensive inventories of typeface, symbols, logos, trademarks and other indicia. In addition, the invention contemplates the consumer purchasing blank carrier sheets and provides him with the flexibility of providing whatever characters he desires to place on the surface of the carrier sheet, whenever he requires the same.